1. Field of the Invention
This invention is related to a peak voltage detector with a ferroelectric element, and in particular to a device which can detect the peak voltages output by sensing devices such as light sensors, heat sensors, pressure sensors and the like without the need for a reference voltage.
2. Description of the Related Art
Generally, sensing devices such as light, heat, pressure and wind sensors sense the varying physical amounts by generating a voltage corresponding to the amount of light, heat or pressure to be detected. Conventionally, a comparator (10) such as that shown in FIG. 1 for example, could be used to detect the fact that these voltages have exceeded the reference voltage value. The comparator (10) consists of the well-known current mirror circuit (10a) and a differential circuit (10b) arranged in such a way that the output of comparator (10) represents the difference in voltage between the input terminal and the inverting input terminal. Therefore, by applying the designated reference voltage to the inverting input terminal and inputting the output voltage from light sensors, heat sensors and the like to the input terminal it is possible to monitor whether or not the externally applied sensing voltage exceeds the predetermined reference voltage.
However, in using voltage measuring devices such as this kind of comparator in the prior art, there is a problem where if the external power supply (10c) is defective the comparator gives an invalid output. Therefore, in order to monitor peak voltages, it is usually necessary to connect an external memory to the output of the comparator to maintain continuity in the output, resulting in further complication of the construction of the device.